cmake: add -fno-omit-frame-pointer to CXX Debug flags

Signed-off-by: Thomas Ingleby <thomas.c.ingleby@intel.com>
mraa_internal: add extern "C" to internal headers

Signed-off-by: Thomas Ingleby <thomas.c.ingleby@intel.com>
hook: rename from declared struct to adance_func

* Removed bitfield, now checks if pointer NULL.

Signed-off-by: Thomas Ingleby <thomas.c.ingleby@intel.com>
hook: change header of board definition, add internal

Signed-off-by: Thomas Ingleby <thomas.c.ingleby@intel.com>
Merge branch 'hook'

Conflicts:
	include/intel_galileo_rev_d.h
	include/intel_galileo_rev_g.h
	include/mraa_adv_func.h
	include/mraa_internal.h
	src/gpio/gpio.c
	src/mraa.c